Thornton will probably end up with 10. He's never had discipline (or even a hearing) before in his career, that will work for him, and maybe if Orpik had been able to get up, he would have only gotten a slap on the wrist. Even if he had merely knocked him out with the slewfoot and falling on him, then probably 3-5. But hitting him again after he was out is dangerous and malicious, and I'm sure he regrets it, but he's going to do the time. As well, even though it is still largely codified by the players, the league itself is trying to shed this wild west image of on ice enforcement. If Thornton had a history of stuff like this, he'd be seeing 20 easily.
I'd also guess his teammates will pitch in to cover some of his missing salary, even though we won't hear about it. As I've said elsewhere, the Penguins were basically broadcasting that they thought they could do anything they wanted to the Bruins and the refs were saying "please do" and Thornton tried to go about it the "right way" first and got penalized for it, and the Penguins got a goal for it. So basically the league, through its rules and endorsement of the refs, was saying "not only can you take runs at Bruins players, but we will reward you when they try to retaliate." And finally Thornton lost his shit. But you can't lose your shit, and he will be penalized appropriately.